Effective preventive strategies require early detection of sub-clinical atherosclerotic heart disease. Radiographic detection and quantification of coronary artery calcium has undergone extensive research in this regard. There is a strong association between coronary calcium and both pathologic findings and coronary events. Most recent research has utilized computed tomography for evaluating coronary calcium. Fluoroscopic evaluation is limited by low sensitivity, due to interfering background tissue structures and inability to objectively quantify calcium content. Dual energy imaging does not suffer from these two limitations and offers a lower dose and lower cost solution to early detection of atherosclerosis. The proposed research will develop a motion insensitive dual energy subtraction technique that will provide densitometry measurements of coronary calcium. More specifically, the aims are: (1) Investigation of the hypothesis that the absolute calcium mass in coronary arteries can be accurately measured using a densitometry technique with phantom and animal studies. The densitometry analysis will be performed on tissue suppressed dual energy images and will yield absolute (as opposed to relative) calcium mass. (2) To test the hypothesis that calcium mass measured in human volunteers with dual-energy fluoroscopy and calcium score measured with electron beam computed tomography have a Spearman correlation coefficient higher than 0.95. (3) To establish the presence or absence of a difference between the two technologies in discriminating persons with prevalent coronary heart disease from those without prevalent coronary heart disease. This research will provide a method to non-invasively quantify coronary artery calcium using dual energy imaging. Most likely, cardiac imaging with image intensifier television based systems will be replaced with flat-panel detectors in the coming years. As the rapid development in the last few years has shown, the new digital systems will allow development of more sophisticated analysis techniques. Densitometry based quantification of coronary artery calcium mass is one promising analytical technique that new digital systems may provide. To date, the sensitivity of temporal subtraction to cardiac motion has hampered the development of digital image processing techniques for cardiac imaging. Dual-energy imaging, because of its motion insensitivity, can serve as a foundation for quantitative cardiac analysis to proceed.